The invention relates to a solar cell comprising of a semiconductor body containing a pn-junction, with the thin surface zone of the semiconductor body being of one conduction type and having a metallization, a rear side contact, and a layer for reducing reflection.
Today, mainly monocrystalline or polycrystalline silicon solar cells with an efficiency of approximately 14% are used for the conversion of solar energy into electrical energy. Efficiency losses result, inter alia, from reflection losses, incomplete absorption, partial utilization of the photon energy, recombination of generated charge carriers, and deviation of the energy band gap of the starting material from the ideal optimum of 1.4 eV, etc.
For better utilization of the AM1 spectrum (air mass 1)-solar spectrum after absorption in the atmosphere in relation to sea level when the sun is in its highest position--an efficiency of approximately 22% is obtained with solar cells based on gallium arsenide on account of its almost ideal energy band gap of 1.43 eV. The manufacture of gallium arsenide solar cells is still relatively expensive for mass production.
Tests with amorphous silicon have already been carried out with a view to enabling economical production of solar cells. The reason for this lies in the cost-reduced manufacture of the starting material, in the low material consumption, and also in the possibility of mass production.
With solar cells made from amorphous silicon, however, an efficiency of only 5.5% was obtained for cells made in a continuous production process. Also the efficiency of monocrystalline or polycrystalline silicon solar cells is still unsatisfactory.